We study sulfur metabolism using skin fibroblasts and have concentrated on the following areas: 1. Study of the treatment of cystinosis with cysteamine, pantethine and WR-1065. The latter two compounds lower cystine levels in cystinotic cells, as does cysteamine but are less toxic than cysteamine. Pantethine is being used in a clinical trial, so methods for detection in serum and uring are being developed. 2. Efforts to define the source of cystinotic cystine by way of the study of metallothionine, a protein that contains one third cysteine residues and was found in 35S-cystine labeled cystinotic cells at levels two fold that found in normal cells. 3. Discovery and investigation of a mutant mouse which stores cystine in lysosomes as do cystinotic patients. Possible anomalines in cholesterol metabolism are being investigated. 4. Continued study of the glutathione cycle which when manipulated with inhibitors or stimulators will directly vary the cystine levels in cystinotic cells. 5. Availability of diagnostic service for detection of cystinosis in new cases.